Pad Conditioner and Method for Making the Same

ABSTRACT

A method for making a pad conditioner, includes: (a) providing a first substrate having a grain-mounting surface, and a plurality of diamond abrasive grains, each of which has a retained portion and a cutting portion with at least one sharp corner; (b) forming a plurality of recesses in the first substrate, each of the recesses having a sharp closed end and an enlarged open end, and diverging from the sharp closed end to the enlarged open end in a manner to have a shape corresponding to that of the sharp corner of each of the diamond abrasive grains; (c) disposing each of the diamond abrasive grains in a respective one of the recesses; (d) forming a second substrate on the grain-mounting surface of the first substrate; and (e) removing the first substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese application no. 096129008,filed on Aug. 7, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for making a pad conditioner, moreparticularly to a method involving forming pyramid and/or frusto-pyramidrecesses for receiving sharp corners of diamond abrasive grains therein,respectively.

2. Description of the Related Art

Chemical Mechanical Polishing (CMP) is a well-known method that caneffectively and reliably achieve global planarization of a wafer surfacefor under 0.5 μm technology. The growth of CMP techniques is attributedto a need to solve a light-focus problem of photolithography resultingfrom miniaturization of ICs, and to an increase in the number of layersof a multi-layered structure in ICs.

Performance of a CMP process is mainly affected by a pad conditioner,which is used to condition a polishing pad, i.e., to form a stablestructure of pad asperities on the polishing pad. Wafer polishing occursat an interface among the pad asperities, the wafer surface, and aslurry. Thus, the quality of the pad conditioner is a key factor fordetermining the performance of a CMP process, such as material removalrate, removal stability, planarization and defectivity.

Conventional methods for making the pad conditioner include attaching aplurality of diamond abrasive grains to a substrate surface using apatterned template or sieve. However, orientations of the diamondabrasive grains on the substrate surface are randomly disposed using thepatterned template or sieve, which results in large height variationsfor top ends of the diamond abrasive grains relative to the substratesurface. An average height difference among the top ends of the diamondabrasive grains of the conventional pad conditioner thus formed usuallyranges at least from 50 μm to 100 μm. Consequently, grooves formed inthe polishing pad through the diamond abrasive grains of theconventional pad conditioner have various depths relative to thesurface, which causes problems, such as polishing uniformity, highdefectivity, and short service life. In addition, since the heightdifference is large, only a small portion of the diamond abrasive grains(i.e., working diamonds) are effective in forming the grooves in thepolishing pad, which causes excessive wearing for the small portion ofthe diamond abrasive grains, and which results in a decrease in thecutting rate for forming the grooves in the polishing pad.

Moreover, commercial diamond abrasive grains are normally cuboctahedronin shape (see FIGS. 1 a to 1 d), and have sharp corners (i.e., pointedcorners 913 and linear corners 914), and {111} and {100} faces 911, 912.FIG. 2 illustrates configurations of different grooves formed by thepointed corner 913, the linear corner 914, and the {111} and {100} faces911, 912 of a diamond abrasive grain 4, respectively. Since the groovesformed by the pointed corner 913 and the linear corner 914 of thediamond abrasive grain 4 are narrow and deep, the pad asperities of thepolishing pad 81 thus formed are thick and have a high mechanicalstrength, which, in turn, can achieve a high performance in materialremoval rate and a relatively low defectivity. On the contrary, sincethe grooves formed by the {111} and {100} faces 911, 912 of the diamondabrasive grain 4 are wide and shallow, the pad asperities of thepolishing pad 81 thus formed are thin and have a weak mechanicalstrength, thereby resulting in a decrease in the material removal rateand an increase in the defectivity. Hence, the orientation of each ofthe diamond abrasive grains 4 is preferably arranged in a manner thatthe top end of each of the diamond abrasive grains 4, which is to be incontact with the polishing pad 81 during a cutting operation, is thepointed corner 913 or the linear corner 914. As such, the higher thenumber of the pointed corners 913 and/or the linear corners 914 disposedas the top ends of the diamond abrasive grains 4, the higher will be theperformance of the pad conditioner in cutting the polishing pad 81, andthe better will be the quality of the polishing pad 81 thus formed.

U.S. Pat. No. 6,769,975 discloses a method for forming a padconditioner. The method involves forming a plurality of holes in aspacer, each of which has a cylindrical portion having a diametersmaller than the average particle diameter of the diamond abrasivegrains, and a bowl-shaped upper portion enlarged in dimensions from thecylindrical portion to a top end of the spacer. After disposing thediamond abrasive grains in the holes, a bonding layer at an upper faceof the spacer is formed so as to enclose and bond to the diamondabrasive grains, and the spacer is then removed to expose a portion ofeach of the diamond abrasive grains, that serves to cut a polishing pad.Although the quality of the pad conditioner thus formed is improved,there is still a need for further improving the aforesaid heightdifference problem and increasing the number of the pointed corners 913and/or the linear corners 914 disposed as the top ends of the diamondabrasive grains 4 of the pad conditioner.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a methodfor making a pad conditioner that can overcome the aforesaid drawbacksassociated with the prior art.

Another object of this invention is to provide a pad conditioner made bythe method.

According to the present invention, a method for making a padconditioner, comprises: (a) providing a first substrate having agrain-mounting surface, and a plurality of diamond abrasive grains, eachof which has a retained portion and a cutting portion with at least onesharp corner; (b) forming a plurality of recesses in the firstsubstrate, each of the recesses being indented from the grain-mountingsurface, having a sharp closed end and an enlarged open end opposite tothe sharp closed end, and diverging from the sharp closed end to theenlarged open end in a manner to have a shape corresponding to that ofthe sharp corner of the cutting portion of each of the diamond abrasivegrains; (c) disposing each of the diamond abrasive grains in arespective one of the recesses such that the cutting portion of each ofthe diamond abrasive grains is received in the respective recess, andthat the retained portion of the respective one of the diamond abrasivegrains protrudes outwardly of the grain-mounting surface of the firstsubstrate; (d) forming a second substrate on the grain-mounting surfaceof the first substrate in such a manner to enclose and bond to theretained portion of each of the diamond abrasive grains; and (e)removing the first substrate.

According to another aspect of this invention, a pad conditionercomprises: a substrate having a surface; and a plurality of diamondabrasive grains, each of which has a top portion protruding from thesurface of the substrate. The top portion has a top end with a heightrelative to the surface of the substrate. A height difference between ahighest one of the top ends of the top portions of the diamond abrasivegrains and a lowest one of the top ends of the top portions of thediamond abrasive grains is less than 40 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiment of this invention, with reference to the accompanyingdrawings, in which:

FIGS. 1 a-1 d are perspective views of commercial crystal diamondabrasive grains;

FIG. 2 is a fragmentary partly sectional view to illustrateconfigurations of cutting grooves in a polishing pad cut by differentportions of the diamond abrasive grains;

FIG. 3 is a schematic view of a die used for making recesses in a firstsubstrate according to the preferred embodiment of a method for making apad conditioner of this invention;

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIG. 5 is a schematic view of the first substrate formed with therecesses using the die of FIG. 3 according to the preferred embodiment;

FIG. 6 is a sectional view taken along line VI-VI in FIG. 5;

FIG. 7 is a fragmentary sectional view to illustrate how an adhesive isapplied in the recesses in the first substrate according to thepreferred embodiment;

FIGS. 8 and 9 are fragmentary sectional views to illustrate how thediamond abrasive grains are disposed in the recesses in the firstsubstrate according to the preferred embodiment;

FIGS. 10 and 11 are sectional views to illustrate how a second substrateis formed to bond to the diamond abrasive grains according to thepreferred embodiment;

FIG. 12 is a fragmentary perspective view of the preferred embodiment ofa pad conditioner formed according to the method of this invention;

FIG. 13 is a fragmentary partly sectional view of FIG. 12;

FIG. 14 is a microscope image of the pad conditioner of Example 1;

FIG. 15 is a surface profile-measuring graph showing heights of aportion of the diamond abrasive grains of Example 1;

FIG. 16 is a microscope image of the pad conditioner of Example 2;

FIG. 17 is a surface profile-measuring graph showing heights of aportion of the diamond abrasive grains of Example 2;

FIG. 18 is a microscope image of the pad conditioner of Example 3; and

FIG. 19 is a surface profile-measuring graph showing heights of aportion of the diamond abrasive grains of Example 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 3 to 12 illustrate consecutive steps of the preferred embodimentof a method for making a pad conditioner 100 according to thisinvention. The method includes: (a) providing a first substrate 11 (seeFIG. 5) having a grain-mounting surface 13, and a plurality of diamondabrasive grains 4, each of which has a retained portion 40 and a cuttingportion with at least one sharp corner 913, 914 (see FIG. 8) and atleast one of {111} and {100} faces 911, 912 (see FIGS. 1 a to 1 d); (b)forming a plurality of recesses 12 in the first substrate 11 (see FIGS.5 and 6) using a die 2 (see FIGS. 3 and 4), each of the recesses 12being indented from the grain-mounting surface 13, having a sharp closedend 121 and an enlarged open end opposite to the sharp closed end 121,and diverging from the sharp closed end 121 to the enlarged open end ina manner to have a shape corresponding to that of the sharp corner 913,914 of the cutting portion of each of the diamond abrasive grains 4; (c)disposing each of the diamond abrasive grains 4 in a respective one ofthe recesses 12 (see FIGS. 8 and 9) such that the cutting portion ofeach of the diamond abrasive grains 4 is received in the respectiverecess 12, and that the retained portion 40 of the respective one of thediamond abrasive grains 4 protrudes outwardly of the grain-mountingsurface 13 of the first substrate 11; (d) forming a second substrate 6on the grain-mounting surface 13 of the first substrate 11 (see FIGS. 10and 11) in such a manner to enclose and bond to the retained portion 40of each of the diamond abrasive grains 4; and (e) removing the firstsubstrate 11 (see FIG. 11).

Preferably, each of the diamond abrasive grains 4 is substantiallycuboctahedron in shape.

By virtue of the geometric interference between each of the diamondabrasive grains 4 and a recess-defining wall of each of the respectiverecess 12, the shape of the recesses 12 thus constructed facilitatesentrance of the sharp corner 913, 914 of the cutting portion of each ofthe diamond abrasive grains 4 into the sharp closed end 121 of therespective recess 12 during disposing of the diamond abrasive grains 4in the respective recesses 12. In this embodiment, the recesses 12 arepreferably pyramidal in shape, such as a right pyramid, a right cone anda right circular cone. Alternatively, the recesses 12 can befrusto-pyramidal in shape.

Preferably, the sharp closed end 121 of each of the recesses 12 has anangle ranging from 60° to 120°.

Preferably, each of the recesses 12 has a depth 122 relative to thegrain-mounting surface 13 of the first substrate 11 that ranges from0.25 to 0.95 times an average particle diameter of the diamond abrasivegrains 4.

In this embodiment, the method further includes applying an adhesive 31in each of the recesses 12 prior to step (c) so as to adhere the cuttingportion of each of the diamond abrasive grains 4 in the respective oneof the recesses 12 to the first substrate 11, and removing the adhesive31 after step (e) for exposing the cutting portion of the diamondabrasive grains 4.

Preferably, application of the adhesive 31 to the first substrate 11 isconducted through one of screen printing, dispensing, spraying, and inkjet techniques.

Preferably, the applied adhesive 31 in the respective recess 12 has aheight 311 relative to the sharp closed end 121, which is 0.1-0.9 timesthe depth 122 of the recesses 12, and more preferably, 0.2-0.6 times thedepth 122 of the recesses 12. When the height 311 is less than 0.1 timesthe depth 122 of the recesses 12, the cutting portion of each of thediamond abrasive grains 4 is likely to fail to make contact with or toonly make slight contact with the adhesive 31. When the height 311 ismore than 0.9 times the depth 122 of the recesses 12, the function ofthe shape of each of the recesses 12, which serves to guide the sharpcorner 913, 914 of the cutting portion of the respective diamondabrasive grain 4 to enter the sharp closed end 121 of the recess 12,will be completely lost.

Preferably, the adhesive 31 is selected from the group consisting ofnatural rubber, neoprene rubber, acrylic ester, silicone, polyurethane,and combinations thereof.

In this embodiment, the second substrate 6 is made from a resin.Preferably, the resin is one of a thermosetting resin and athermoplastic resin. Preferably, the thermosetting resin is selectedfrom the group consisting of unsaturated polyester resin, vinyl esterresin, epoxy resin, phenolic resin, bismaleimide, polyimide, andcombinations thereof. More preferably, the thermosetting resin is epoxyresin.

In this embodiment, each of the diamond abrasive grains 4 has a particlediameter ranging from 10 mesh to 140 mesh.

Referring to FIGS. 12 and 13, the pad conditioner 100 formed accordingto the method of this invention includes: the second substrate 6 havinga surface 62; and a plurality of the diamond abrasive grains 4, each ofwhich has a top portion 45 protruding from the surface 62 of thesubstrate 6. The top portion 45 has a top end with a height 44 relativeto the surface 62 of the substrate 6. A height difference between ahighest one of the top ends of the top portions 45 of the diamondabrasive grains 4 and a lowest one of the top ends of the top portions45 of the diamond abrasive grains 4 is less than 40 μm. Since thediamond abrasive grains 4 are randomly disposed on the first substrate11 during preparation of the pad conditioner 100, probability for eachof the sharp corners 913, 914 and at least one of the {111} and {100}faces 911, 912 to enter into the sharp closed end 121 or a lower spaceof the recess 12 is likely the same. However, by virtue of the shape ofthe recesses 12, most of the top ends of the top portions 45 of thediamond abrasive grains 4 of the pad conditioner 100 are the sharpcorners 913, 914. The percentage of the number of the diamond abrasivegrains 4 with the sharp corners 913, 914 as the top ends can be up toabout 90%.

The merits of the method for making the pad conditioner 100 of thisinvention will become apparent with reference to the following Examples.

EXAMPLE Example 1

A die 2 made by wire cutting techniques was provided to imprint aplastic substrate 11 so as to form a plurality of pyramidal recesses 12therein (FIGS. 3-5). The die 2 was made from a stainless steel plate 21that was formed with a plurality of right pyramids 22 protruding from adie surface 211 of the stainless steel plate 21 having a diameter of 110mm and a thickness of 30 mm. The right pyramids 22 were distributed overa region with a diameter of 100 mm on the die surface 211. The distancebetween tip ends 221 of each two adjacent ones of the right pyramids 22was 700 μm. The tip end 221 of each of the right pyramids 22 defined anangle of about 90° and a height of 350 μm relative to the die surface211. The plastic substrate 11 was made from polypropylene, and had adiameter of 110 mm and a thickness of 0.4 mm. A pressure of 10 MPa wasapplied on the die 2 to imprint the plastic substrate 11 so as to formabout 15785 pyramidal recesses 12, each of which defined an angle of90°, a depth 122 of 225 μm relative to a surface 13 of the plasticsubstrate 11, and a width 123 of 450 μm. The distance between the sharpclosed ends 121 of each two adjacent ones of the pyramidal recesses 12was 700 μm.

It is noted that formation of the pyramidal recesses 12 can also beconducted through injection molding or die casting, or throughelectronic discharge machining, ultrasonic machining, micro-milling,laser machining, electron beam machining, and ion beam machiningtechniques, which can dispense with the die 2.

A stainless steel screen 32 having a thickness of 50 μm and formed withcircular holes 321 of 0.2 mm in diameter was disposed on the plasticsubstrate 11. An adhesive 31 was formed by mixing a water-based acrylicpressure sensitive adhesive (SP-7533, produced by 3M CO.) and deionizedwater at a weight ratio of 1:1. The adhesive 31 was applied to thestainless steel screen 32, and was forced into the pyramidal recesses 12using a scraper 34. The plastic substrate 11 was then placed in a hotrecirculating oven under a temperature of 50° C. for 15 min. The height311 of the adhesive 31 in the recess 12 relative to the sharp closed end121 of the recess 12 was about 50 μm (FIG. 8).

A plurality of the diamond abrasive grains 4 having a cuboctahedronshape with a particle diameter ranging from 40 mesh to 45 mesh (SDB1100,produced by ELEMENTSIX) were distributed over the plastic substrate 11,and were moved into the recesses 12 using an acrylic brush so as to bebonded to the adhesive 31 in the recesses 12.

It is noted that moving of the diamond abrasive grains 4 into therecesses 12 can also be conducted using an oscillator.

Excess diamond abrasive grains 4 were removed from the plastic substrate11 using the brush or using the oscillator.

A pressing plate 35 of silicon was then disposed on the diamond abrasivegrains 4 on the plastic substrate 11, and a pressure of 0.2 MPa wassubsequently applied on the pressing plate 35 to force the diamondabrasive grains 4 into the recesses 12 so as to ensure that the sharpcorners 913, 914 of the diamond abrasive grains 4 are fully received inthe sharp closed ends 121 of the recesses 12 (FIG. 7).

The pressing plate 35 can also be made from an elastomeric material,such as natural rubber or polyvinyl chloride.

Preferably, the pressure applied on the pressing plate 35 ranges from0.1 MPa to 1 MPa.

The plastic substrate 11 having the diamond abrasive grains 4 attachedthereto was disposed in a mold 5. The mold 5 was vacuumed to lower than1 mbar. A thermosetting resin was then injected into the mold 5 so as toform the second substrate 6 to bond to the diamond abrasive grains 4.The thermosetting resin was formed by mixing epoxy resin (EPOFIX RESIN,produced by STRUERS A/S Co.) and a curing agent (EPOFIX HARDENER,produced by STRUERS A/S Co.) at a weight ratio of 25:3.

It is noted that vacuuming of the mold 5 has an advantage in removingair in the mold 5 and the recesses 12 so as to prevent formation ofpores between the diamond abrasive grains 4 and thermosetting resin.

After the thermosetting resin was hardened under room temperature for 12hours, the plastic substrate 11 together with the diamond abrasivegrains 4 and the second substrate 6 (FIG. 11) was removed from the mold5, and was subsequently removed from the second substrate 6. The diamondabrasive grains 4 on the second substrate 6 was then dipped in a methylethyl ketone solvent for 15 min, and was cleaned with a scrubbing rollerso as to remove the adhesive 31 on the diamond abrasive grains 4 forexposing the cutting portions of the diamond abrasive grains 4. Afterfurther cleaning using an ultrasonic instrument and drying throughcompressed air, a pad conditioner 100 including the second substrate 6and the diamond abrasive grains 4 was obtained.

It is noted that a release agent, such as polyvinyl alcohol,polytetrafluoroethylene, dimethyl polysiloxane and wax, is preferablyused to coat an inner surface of the mold 5 and the surface 13 of theplastic substrate 11 so as to facilitate separation of the plasticsubstrate 11 from the mold 5. Removal of the adhesive 31 can also beconducted through soaking in ethanol or dimethyl benzene solvent, orwater washing with a non-abrasive roller.

Since the thermosetting resin injected into the mold 5 also fills theremaining portion 124 of each recess 12 (see FIG. 8) in the plasticsubstrate 11, which is not occupied by the adhesive 31 and the diamondabrasive grain 4, a protrusion 61 of the thermosetting resin is formedand protrudes from the second substrate 6 after formation of the secondsubstrate 6, thereby enhancing bonding between the second substrate 6and the diamond abrasive grains 4.

FIG. 14 is a microscope image showing a configuration of the padconditioner 100 of Example 1 at 60× magnification.

By examining about 1000 diamond abrasive grains 4 of the pad conditioner100 via observing the microscope image, the number of the diamondabrasive grains 4 with the sharp corners 913, 914 as the top ends was890, i.e., the percentage of the number of the diamond abrasive grains 4with the sharp corners 913, 914 as the top ends was 89%.

FIG. 15 is a surface profile-measuring graph showing the heights 44 of aportion of the diamond abrasive grains 4 of Example 1 using a surfaceprofile-measuring instrument (MITUTOYO, SURFTEST SV-400). The parametersset for measuring the heights 44 of the diamond abrasive grains 4 are asfollows: The height to be measured was 600 μm. The resolution was 0.1μm. The length to be measured was 5.0 mm. Each peak represented theheight 44 of each of the measured diamond abrasive grains 4. The maximumheight difference between the highest peak and the lowest peak was lessthan 25 μm, which is an indication of relatively uniform heights 44 forthe diamond abrasive grains 4 on the pad conditioner 100 of Example 1.

Example 2

The pad conditioner 100 of Example 2 was prepared by steps similar tothose of Example 1, except that the height 311 of the adhesive 31relative to the sharp closed end 121 of the recess 12 was about 150 μm(see FIG. 8).

FIG. 16 is a microscope image showing a configuration of the padconditioner 100 of Example 2 at 60× magnification. Since the height 311of the adhesive 31 in the recess 12 of Example 2 was higher than that ofExample 1, the height of the protrusions 61 of Example 2 was smallerthan that of Example 1. By examining about 1000 diamond abrasive grains4 of the pad conditioner 100 via observing the microscope image, thenumber of the diamond abrasive grains 4 with the sharp corners 913, 914as the top ends was 810, i.e., the percentage of the number of thediamond abrasive grains 4 with the sharp corners 913, 914 as the topends was 81%.

FIG. 17 is a surface profile measuring graph showing the heights 44 of aportion of the diamond abrasive grains 4 of Example 2 using the surfaceprofile-measuring instrument (MITUTOYO, SURFTEST SV-400). The parametersset for the measurement were the same as those of Example 1. The maximumheight difference was 15 μm, which is an indication of relativelyuniform heights 44 for the diamond abrasive grains 4 on the padconditioner 100 of Example 2.

Example 3

The pad conditioner 100 of Example 3 was prepared by steps similar tothose of Example 1, except for the manners of making the plasticsubstrate 11 and filling the adhesive 31.

The die 2 was formed by V-shaped groove grinding machining techniques,in which an annular region (which has an inner radius of 23.6 mm and anouter radius of 51.3 mm) of a stainless steel (SUS420) body was cut andground from three directions (each direction pair forming an angle of120 degrees) so as to form a plurality of V-shaped grooves in eachdirection. The distance between each two adjacent ones of the V-shapedgrooves was 1.23 mm. The grinding angle was 70.52°. The depth 122 of theV-shaped grooves was about 0.577 mm.

A pressure of 10 MPa was then applied on the die 2 thus formed toimprint the plastic substrate 11 (polypropylene), which had a diameterof 110 mm and a thickness of 1.0 mm, so as to form 7192 right-conerecesses 12 therein, each of which defined an angle of 90°, and a depth122 of 350 μm relative to the surface 13 of the plastic substrate 11.

The adhesive 31 was then filled in the recesses 12 through dispensingtechniques using a needle. An inner diameter of the needle of thedispensing machine was 0.26 mm. The adhesive 31 was formed by mixingwater-based acrylic pressure sensitive adhesive (SP-7533, produced by 3MCO.) and deionized water at a weight ratio of 2:1. The height 311 of theadhesive 31 relative to the sharp closed end 121 of the recess 12 wasabout 200 μm after drying. The particle diameter of the diamond abrasivegrains 4 ranged from 30 mesh to 35 mesh (SDB1100, produced byELEMENTSIX).

FIG. 18 is a microscope image showing a configuration of the padconditioner 100 of Example 3 at 60× magnification. By examining about500 diamond abrasive grains 4 of the pad conditioner 100 via observingthe microscope image, the number of the diamond abrasive grains 4 withthe sharp corners 913, 914 as the top ends was 415, i.e., the percentageof the number of the diamond abrasive grains 4 with the sharp corners913, 914 as the top ends was 83%.

FIG. 19 is a surface profile measuring graph showing the heights 44 of aportion of the diamond abrasive grains 4 of Example 3 using the surfaceprofile-measuring instrument (MITUTOYO, SURFTEST SV-400). The parametersset for the measurement were the same as those of Example 1, except thatthe length to be measured was 7.5 mm. The maximum height difference was20 μm.

Since the maximum height difference is relatively small for the padconditioner 100 of this invention, more diamond abrasive grains 4 canserve as the working diamonds as compared to the conventional padconditioner, which improves the cutting rate, removal stability, andservice life of the polishing pad processed by the pad conditioner 100.

Moreover, the percentage of the number of the diamond abrasive grains 4with the sharp corners 913, 914 as the top ends is much higher ascompared to that of the conventional pad conditioner, thereby improvingproduction of good quality polishing pads.

With the invention thus explained, it is apparent that variousmodifications and variations can be made without departing from thespirit of the present invention. It is therefore intended that theinvention be limited only as recited in the appended claims.

1. A method for making a pad conditioner, comprising: (a) providing afirst substrate having a grain-mounting surface, and a plurality ofdiamond abrasive grains, each of which has a retained portion and acutting portion with at least one sharp corner; (b) forming a pluralityof recesses in the first substrate, each of the recesses being indentedfrom the grain-mounting surface, having a sharp closed end and anenlarged open end opposite to the sharp closed end, and diverging fromthe sharp closed end to the enlarged open end in a manner to have ashape corresponding to that of the sharp corner of the cutting portionof each of the diamond abrasive grains; (c) disposing each of thediamond abrasive grains in a respective one of the recesses such thatthe cutting portion of each of the diamond abrasive grains is receivedin the respective recess, and that the retained portion of therespective one of the diamond abrasive grains protrudes outwardly of thegrain-mounting surface of the first substrate; (d) forming a secondsubstrate on the grain-mounting surface of the first substrate in such amanner to enclose and bond to the retained portion of each of thediamond abrasive grains; and (e) removing the first substrate.
 2. Themethod of claim 1, wherein the sharp closed end of each of the recesseshas an angle ranging from 60 to 120°.
 3. The method of claim 2, whereineach of the recesses has a depth relative to the grain-mounting surfaceof the first substrate that ranges from 0.25 to 0.95 times an averageparticle diameter of the diamond abrasive grains.
 4. The method of claim3, further comprising applying an adhesive in each of the recesses priorto step (c) so as to adhere the cutting portion of each of the diamondabrasive grains in the respective recess to the first substrate.
 5. Themethod of claim 4, further comprising removing the adhesive after step(e) for exposing the cutting portions of the diamond abrasive grains. 6.The method of claim 5, wherein the applied adhesive in each of therecesses has a height relative to the sharp closed end, which is 0.1-0.9times the depth of the recesses.
 7. The method of claim 6, wherein theheight of the applied adhesive in each of the recesses is 0.2-0.6 timesthe depth of the recesses.
 8. A pad conditioner comprising: a substratehaving a surface; and a plurality of diamond abrasive grains, each ofwhich has a top portion protruding from said surface of said substrate,said top portion having a top end with a height relative to said surfaceof said substrate; wherein a height difference between a highest one ofsaid top ends of said top portions of said diamond abrasive grains and alowest one of said top ends of said top portions of said diamondabrasive grains is less than 40 μm.
 9. The pad conditioner of claim 8,wherein said substrate is made from a resin.